But members of Australia's Cambodian community are pushing ahead with plans to stage protests against a man they say is a "dictator" who "rules Cambodia with an iron fist".

Addressing a rally late last month, the Cambodian Prime Minister directed his threats at anyone thinking of burning an effigy of him while he attends the Sydney summit.

"I want to make this clear," Hun Sen said.

"If you have the right to burn me, we have our right to beat you up. There is nothing wrong with that. I will follow them home and grab them."

Hun Sen, a regional strongman who has been in power for more than three decades, made the comments in reference to his trip to Sydney at the invitation of the Australian Government to attend a special gathering of South-East Asian leaders.

The summit will also see Myanmar's leader Aung San Suu Kyi visit Australia, one of her first foreign appearances since the controversy erupted on the international stage over the treatment of Rohingya Muslims in Myanmar.

Jimmy Neam, who fled Cambodia for Australia in the 1980s, said Hun Sen should "not be in Australia at all".

"I believe he's got a lot of blood on his hands, I think he's a dictator," he said.

He said dialogue with the Cambodian Prime Minister was futile.

"Engagement is good, if you engage in a productive way," he said.

"But we know Hun Sen … he rules the country with an iron fist."

When Vandy Kang first heard about Hun Sen's comments, he was "very upset and very angry".

Mr Kang, 63, came to Australia in 1983 as a refugee.

He tears up still thinking of life under the Khmer Rouge regime of 1970s Cambodia, during which 2 million people died, including his mother and two brothers.

He said Hun Sen's threats would not stop protests going ahead.

"Under the Khmer Rouge, I could not say anything that I wanted to say because we were forbidden from speaking up to express our ideas," he said.

"So now is an opportunity for me and all of us to stand up against Hun Sen."

The threats made by the Cambodian leader nevertheless stoke fear.

Vandy Kang said he was "very concerned".

Hun Sen, he said, "may not be able to come and chase us, but his supporters in Australia may do something, because they are ignorant people, they would follow his orders".

"Anyway, we have to stand up and try to challenge that aggression," he said.

As outlandish as they sound in the Australian context, Hun Sen's comments are "par for the course in Cambodia", according to Lee Morgenbesser, a lecturer at Griffith University's Asia Institute.

"It mainly plays for domestic reasons rather than international reasons," Mr Morgenbesser said.

"Hun Sen likes to sell the narrative in Cambodia that Cambodia is under threat from hostile foreign nations such as the United States, and to a lesser extent Australia.

"He likes to sell the idea that only he can protect and defend Cambodia from these threats."

Late last year Hun Sen used the courts to dissolve Cambodia's main opposition party, the Cambodia National Rescue Party, ahead of elections scheduled for later this year.

The party's leader Kem Sokha was arrested and charged with treason and many of the party's other senior figures fled the country, including Vice-President Mu Sochua.

On a visit last week to Australia as a guest of the Australian National University, Ms Sochua appealed to Australia to send a strong message to the Cambodian Prime Minister at the ASEAN meeting.

"Democracy in Cambodia is dead," she told the ABC, "so what are we waiting for?"

Ms Sochua called for Australia to follow the US and European Union in considering tougher targeted sanctions, calling for the assets in Australia of high-ranking Cambodian officials to be frozen.

"We know that these assets are money that has been taken from the blood and sweat of people in Cambodia," she said.

"Even if he's Prime Minister, he will not come to our country and behave like that," Mr Bowen said.

The Australian Government has not commented directly, but in a statement said: "Australia, as a liberal democracy, supports freedom of expression, including the right to protest. It goes without saying that violence, or the threat of violence, is not acceptable in Australia."

At the Bonnyrigg temple, Khim An Chy, who came to Australia in 1980, said she was "not proud" that the Australian Government invited Hun Sen to this country.

"In the future, they shouldn't host that sort of summit in Australia when you have leaders like those types," she said.

World partners:

This service includes material from AAP, Agence France-Presse, APTN, BBC, CNN, Getty, Pacnews, Reuters and other agencies which is copyright and cannot be reproduced, broadcast, rewritten or redistributed without written consent.